Here's one of my favourite quickie meals - smoked haddock fillet, sweet potato chips and steamed greens.
For the haddock; I sprinkle the top with breadcrumbs then pour a mix of melted butter and lemon juice onto the breadcrumbs. Let that soak in then roast the haddock in an oven at 160c. As soon as the breadcrumbs turn golden brown, take the fish out of the oven and it should be perfectly cooked inside. The breadcrumbs protect the fish so it can handle the high heat.
The sweet potato takes the same amount of time as the fish, so put them in and remove them together. Super simple, v tasty.